A method and an arrangement for ensuring the standstill of a vehicle is known, for example, from EP 375 708 B1 (U.S. Pat. No. 5,129,496). There, the standstill of the vehicle is derived on the basis of the wheel speed signals whereupon a braking force is built up at at least one of the wheel brakes in the sense of a parking brake function. This parking brake function is, however, switched off when the driver switches off the voltage supply for the vehicle control systems. A certainty as to standstill is therefore only guaranteed when the supply voltage is switched on.
It is a task of the invention to provide measures which ensure the standstill of a vehicle for each case.
The SAE paper number 96 10 10 (Adaptive Cruise Control, System Aspects and Development Trends, 1996, by Hermann Winner, Stefan Witte, Werner Uhler and Bernd Lichtenberg) shows a speed control while considering the distance to the vehicle traveling ahead. Here, the driver inputs the desired speed of the vehicle via an operator-controlled lever with the usual functions of road speed controllers. This desired speed is controlled comparable to a conventional road speed controller when there is no vehicle present ahead. A desired acceleration is computed from the difference between the desired speed and the driving speed and this acceleration is made available for controlling the drive unit of the vehicle. If a radar system detects a vehicle traveling ahead, then the distance and relative speed to this vehicle are determined. The control task comprises to control the relative speed to zero and, simultaneously, maintain a speed-dependent desired distance. Parameters for determining the desired distance can be set by the driver. This so-called follow-on controller likewise determines a desired acceleration from the above-mentioned quantities. The desired acceleration values can also be negative so that they correspond to deceleration desired values. These are adjusted by influencing the engine of the vehicle and/or the brakes.
Correspondingly, U.S. Pat. No. 5,794,735 shows a road speed controller which inputs a desired acceleration of the vehicle on the basis of the difference between the desired and actual speeds. This desired acceleration is adjusted by controlling the engine and/or by actuating the wheel brakes of the vehicle.
In road speed controller systems of this kind, it can happen that the vehicle is braked to standstill. Here too, it is necessary to make available a guarantee of this standstill.
From U.S. Pat. No. 6,053,584, a procedure is known with the aid of which a comfortable braked stopping of the vehicle is made possible. The braking force at the wheels is reduced somewhat in order to reduce the stopping jolt when there is a drop of a specific vehicle speed in the region of the standstill speed.